13•2Body electrical system
Fuses and circuit breakers- main fuse box (continued)
Fuse NoRating (A)Circuit(s) protected
715 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Instrument illumination, number plate lights
810 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Control circuits for air conditioning, heated windscreen and ride
height control
930 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Headlight washer pump, tailgate and fuel filler flap release
1020 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Central locking system, interior lights, clock, mirror adjustment
1120 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuel pump (with air conditioning), taxi circuits
1210 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Hazard warning flasher
1330 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated seats, cigarette lighters
1430 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Horn
1530 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Wiper motors and screen washer pumps
1630 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated rear window, heated mirrors
1720 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Front foglights
1830 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heater blower
1910 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Accessory circuits
2015 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Direction indicators, reversing lights
2115 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Stop-lights
2210 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Instrument and controls
23C20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Power windows (front) and sliding roof
24C20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Power windows (rear) and rear seat adjustment
C = Circuit breaker
Fuses and circuit breakers - auxiliary fuse box
Colour Rating (A)Circuit(s) protected
Black20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuel-injection pump
Pink20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Air conditioning cooling fan
Yellow20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Anti-lock braking system control circuitry
Green30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Anti-lock braking system pump
Brown30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated windscreen (left-hand side)
Brown30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated windscreen (right-hand side)
GreyC20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Front seat adjustment
Orange20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ride height control
C = Circuit breaker
Relays in main fuse box
IdentificationFunction
I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ignition circuit
II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated rear window and mirrors
III . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Power windows and sliding roof
IV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Seat belt warning
V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Intermittent wipe - front
VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Intermittent wipe - rear
VII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Headlight washer
VIII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Interior light delay
IX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rear seat adjustment
X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Headlights (main beam)
XI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Engine auxiliary
XII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Automatic transmission inhibitor
A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Spare
B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Radio
C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Horn
D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tailgate release
E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Spare
F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Headlights (dipped beam)
G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Seat heaters
H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Front foglights
Other relays and modules
IdentificationFunction
Behind facia (centre):
L1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Lights on buzzer
L2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rear fog light control
L3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Automatic transmission kickdown time
L4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuel pump (with air conditioning)
L5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Hydraulic switch
L6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Anti-theft alarm
Behind facia (passenger side):
M1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Manifold heater (carburettor) or fuel pump (fuel-injection)
M2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Power hold (carburettor) or inspection valve (fuel-injection)
M3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated windscreen (power)
procarmanuals.com
The electrical system is a 12 volt, negative
earth type. Electricity is generated by an
alternator, belt-driven from the crankshaft pulley.
A lead-acid battery provides a reserve of power
for starting and when the demands of the system
temporarily exceed the alternator output.
The battery negative terminal is connected
to “earth” - vehicle metal - and most electrical
system components are wired so that they
only receive a positive feed, the current
returning via vehicle metal. This means that
the component mounting forms part of the
circuit. Loose or corroded mountings can
therefore cause apparent electrical faults.
Many semiconductor devices are used in
the electrical system, both in the “black
boxes” which control vehicle functions and in
other components. Semiconductors are very
sensitive to excessive (or wrong polarity)
voltage, and to extremes of heat. Observe the
appropriate precautions to avoid damage.
Although some repair procedures are given
in this Chapter, sometimes renewal of a well-
used item will prove more satisfactory. The
reader whose interests extend beyond
component renewal should obtain a copy of
the “Automobile Electrical Manual”, available
from the publishers of this book.
Before starting work on the electrical
system, read the precautions listed in “Safety
first!” at the beginning of the manual.
Note:Refer to the precautions given in “Safety
first!” and in Section 1 of this Chapter before
starting work. The following tests relate to testing
of the main electrical circuits, and should not be
used to test delicate electronic circuits (such as
anti-lock braking systems), particularly where an
electronic control unit (ECU) is involved.
General
1A typical electrical circuit consists of an
electrical component, any switches, relays,
motors, fuses, fusible links or circuit breakers
related to that component, and the wiring and
connectors which link the component to both
the battery and the chassis. To help to
pinpoint a problem in an electrical circuit,
wiring diagrams are included at the end of this
Chapter.
2Before attempting to diagnose an electrical
fault, first study the appropriate wiring
diagram, to obtain a more complete
understanding of the components included in
the particular circuit concerned. The possible
sources of a fault can be narrowed down by
noting whether other components related to
the circuit are operating properly. If several
components or circuits fail at one time, the
problem is likely to be related to a shared fuse
or earth connection.
3Electrical problems usually stem from
simple causes, such as loose or corroded
connections, a faulty earth connection, a
blown fuse, a melted fusible link, or a faulty
relay. Visually inspect the condition of all
fuses, wires and connections in a problem
circuit before testing the components. Use the
wiring diagrams to determine which terminal
connections will need to be checked in order
to pinpoint the trouble-spot.
4The basic tools required for electrical fault-
finding include: a circuit tester or voltmeter (a
12-volt bulb with a set of test leads can also
be used for certain tests), a self-powered test
light (sometimes known as a continuity tester),
an ohmmeter (to measure resistance), a
battery and set of test leads, and a jumper
wire, preferably with a circuit breaker or fuse
incorporated, which can be used to bypass
suspect wires or electrical components.
Before attempting to locate a problem with
test instruments, use the wiring diagram to
determine where to make the connections.
5To find the source of an intermittent wiring
fault (usually due to a poor or dirty connection,
or damaged wiring insulation), an integrity testcan be performed on the wiring, which
involves moving the wiring by hand, to see if
the fault occurs as the wiring is moved. It
should be possible to narrow down the source
of the fault to a particular section of wiring.
This method of testing can be used in
conjunction with any of the tests described in
the following sub-Sections.
6Apart from problems due to poor
connections, two basic types of fault can
occur in an electrical circuit - open-circuit or
short-circuit.
7Open-circuit faults are caused by a break
somewhere in the circuit, which prevents
current from flowing. An open-circuit fault will
prevent a component from working, but will
not cause the relevant circuit fuse to blow.
8Short-circuit faults are caused by a “short”
somewhere in the circuit, which allows the
current flowing in the circuit to “escape” along
an alternative route, usually to earth. Short-
circuit faults are normally caused by a
breakdown in wiring insulation, which allows a
feed wire to touch either another wire, or an
earthed component such as the bodyshell. A
short-circuit fault will normally cause the
relevant circuit fuse to blow. Note: A short-
circuit that occurs in the wiring between a
circuit’s battery supply and its fuse will not
cause the fuse in that particular circuit to blow.
This part of the circuit is unprotected - bear
this in mind when fault-finding on the vehicle’s
electrical system.
Finding an open-circuit
9To check for an open-circuit, connect one
lead of a circuit tester or voltmeter to either the
negative battery terminal or a known good earth.
10Connect the other lead to a connector in
the circuit being tested, preferably nearest to
the battery or fuse.
11Switch on the circuit, bearing in mind that
some circuits are live only when the ignition
switch is moved to a particular position.
12If voltage is present (indicated either by
the tester bulb lighting or a voltmeter reading,
as applicable), this means that the section of
2Electrical fault-finding - general
information
1General information
Body electrical system 13•3
13
Other relays and modules (continued)
IdentificationFunction
Behind facia (passenger side) (continued):
M4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heated windscreen (timer)
M5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Air conditioning cooling fan
M6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABS pump relay
M7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABS main relay
M8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABS control unit
M9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ride height control
Below instrument panel (driver’s side):
N1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bulb failure warning unit
Below facia (passenger side):
P1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABS module
P2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuel-injection system module
Behind facia (passenger side):
R1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Speed control system module
R2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Auxiliary warning system module
R3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rear audio console module
Torque wrench settingsNmlbf ft
Alternator adjusting strap:
To steering pump bracket (SOHC) . . . . . . . . . . . . . . . . . . . . . . . . . . .21 to 2616 to 19
To front cover (V6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 to 5130 to 38
procarmanuals.com
the circuit between the relevant connector and
the battery is problem-free.
13Continue to check the remainder of the
circuit in the same fashion.
14When a point is reached at which no
voltage is present, the problem must lie
between that point and the previous test point
with voltage. Most problems can be traced to
a broken, corroded or loose connection.
Finding a short-circuit
15To check for a short-circuit, first disconnect
the load(s) from the circuit (loads are the
components which draw current from a circuit,
such as bulbs, motors, heating elements, etc).
16Remove the relevant fuse from the circuit,
and connect a circuit tester or voltmeter to the
fuse connections.
17Switch on the circuit, bearing in mind that
some circuits are live only when the ignition
switch is moved to a particular position.
18If voltage is present (indicated either by
the tester bulb lighting or a voltmeter reading),
this means that there is a short-circuit.
19If no voltage is present, but the fuse still
blows with the load(s) connected, this
indicates an internal fault in the load(s).
Finding an earth fault
20The battery negative terminal is connected
to “earth” - the metal of the engine/transmission
and the car body - and most systems are wired
so that they only receive a positive feed, the
current returning via the metal of the car body.
This means that the component mounting andthe body form part of that circuit. Loose or
corroded mountings can therefore cause a range
of electrical faults, ranging from total failure of a
circuit, to a puzzling partial fault. In particular,
lights may shine dimly (especially when another
circuit sharing the same earth is in operation),
motors (eg wiper motors or the radiator cooling
fan motor) may run slowly, and the operation of
one circuit may have an apparently-unrelated
effect on another. Note that on many vehicles,
earth straps are used between certain
components, such as the engine/transmission
and the body, usually where there is no metal-to-
metal contact between components, due to
flexible rubber mountings, etc.
21To check whether a component is properly
earthed, disconnect the battery, and connect
one lead of an ohmmeter to a known good
earth point. Connect the other lead to the wire
or earth connection being tested. The
resistance reading should be zero; if not,
check the connection as follows.
22If an earth connection is thought to be
faulty, dismantle the connection, and clean
back to bare metal both the bodyshell and the
wire terminal, or the component’s earth
connection mating surface. Be careful to
remove all traces of dirt and corrosion, then
use a knife to trim away any paint, so that a
clean metal-to-metal joint is made. On
reassembly, tighten the joint fasteners
securely; if a wire terminal is being refitted, use
serrated washers between the terminal and
the bodyshell, to ensure a clean and secure
connection. When the connection is remade,
prevent the onset of corrosion in the future byapplying a coat of petroleum jelly or silicone-
based grease, or by spraying on (at regular
intervals) a proprietary ignition sealer, or a
water-dispersant lubricant.
Headlight
1Open and prop the bonnet. Remove the
cover from the rear of the headlight unit by
twisting it anti-clockwise.
2Disconnect the wiring plug from the
headlight bulb. Release the spring clip by
squeezing its legs together and move it clear
of the bulb (see illustration).
3Remove the headlight bulb (see
illustration). Caution: If the lights have just
been in use, the bulb may be extremely hot.
4When handling the new bulb, use a tissue or
clean cloth to avoid touching the glass with
the fingers. If the glass is accidentally touched,
wipe it clean using methylated spirit. Moisture
and grease from the skin can cause
blackening and rapid failure of the new bulb.
5Fit the new bulb, making sure that the legs
and cut-outs in the bulb base and the reflector
match up. Secure with the spring clip.
6Reconnect the wiring plug. Check the
headlight for correct operation, then refit and
secure the rear cover.
Front parking light (sidelight)
7Gain access as for the headlight bulb, then
pull the parking light bulbholder from the
headlight reflector.
8Extract the wedge base bulb from the
holder (see illustration). Fit the new bulb, refit
the bulbholder and check for correct
operation.
Auxiliary driving light (when fitted)
9From above the auxiliary light unit, release
the cover spring clip and remove the cover
(see illustration).
10Release the spring clip from the bulb.
Withdraw the bulb and unplug its wiring
connector (see illustration). Caution: If the
lights have just been in use, the bulb may be
extremely hot.
11Do not touch the glass of the new bulb
with the fingers.
3Exterior lights - bulb renewal
13•4Body electrical system
3.2 Squeeze the spring clip legs (arrowed)
to remove the headlight bulb3.3 Removing a headlight bulb
3.8 Removing the front parking light bulb
from the holder3.9 Auxiliary driving light cover3.10 Removing the auxiliary driving light
bulb
procarmanuals.com
13•14Body electrical system
16.9 Typical arrangement of relays, control units and module
LHD shown - RHD is mirror image
A Taxi equipment
B Bulb failure module
C EEC IV module
D ABS module
E Rear headphone relay
F Auxiliary warning system control unit
G Speed control system module
H Anti-theft alarm module
I Warning display lighting
K Relay bank
1 Inlet manifold heater relay (carburettor)
2 Fuel pump relay (fuel-injection)
3 Power hold relay (carburettor)
4 Injector relay (fuel-injection)
5 Heated windscreen relay
6 Heated windscreen timer
7 Cooling fan relay (air conditioning)
8 ABS pump relay
9 ABS relay
10 ABS diodes
12 Ride height control relay
12 Day running lights relay (not UK)
procarmanuals.com
17Refit by inserting the switch into the
grommet - use a new grommet if necessary -
and screwing on the retaining ring. Reconnect
the multi-plug and top-up the cooling system.
Washer fluid level switch
18Syphon the fluid out of the washer
reservoir until the level is below the switch.
19Disconnect the switch multi-plug.
Carefully prise the switch out of its grommet
and remove it. Note how flats on the grommet
and switch ensure correct fitting (see
illustration).
20When refitting, make sure that the
grommet is in good condition (renew if
necessary) and is correctly seated. Press the
switch home, reconnect the multi-plug and
refill the reservoir.
Control assembly
Models before April 1992
21Remove the instrument panel surround
and the facia top.
22Remove the two nuts which secure the
assembly(see illustration).Disconnect the
multi-plug by pressing in the locking lever and
pulling the plug. Remove the control
assembly.
23Refit by reversing the removal operations.
Check the AWS for correct operation before
refitting the disturbed trim.
Models from April 1992
24Unclip and remove the right-hand facia
undercover panel.25Carefully prise out the bonnet release lever
surround to gain access to the lever retaining
screws. Undo the three screws then withdraw
the lever. Remove the cable retaining clip and
detach the operating lever from the cable.
26Slacken and remove the five right-hand
lower facia panel retaining screws and remove
the panel from the vehicle.
27Undo the module retaining screw then
disconnect the wiring connectors and remove
the control module from the vehicle (see
illustration).
28Refitting is a reverse of the removal
procedure.
Bulb failure module
Models before April 1992
29Remove the under-dash trim on the
driver’s side. This is secured by six screws,
one of which is only accessible after removing
the air vent grille.
30Pull the module from its bracket.
Disconnect the multi-plug by pressing in the
locking lever and pulling the plug. Remove the
module (see illustration).
31Refit by reversing the removal operations.
Models from April 1992
32Remove the right-hand facia undercover
and lower facia panel.
33The bulb failure module is the right-hand
of the two modules situated directly above the
control pedals. Release the module retaining
clips then disconnect the wiring connector and
remove the module from the vehicle.
34Refitting is a reverse of remova.l
Control switches
1Remove the steering wheel.
2Remove the three screws which secure the
horn contact plate. Disconnect the spade
terminals and remove the contact plate.
3Carefully prise the switch out of the steering
wheel. Disconnect the spade terminals and
remove it.
4Refit by reversing the removal operations.
Vacuum dump valve/switch
5Remove the under-dash trim on the driver’s
side.
6For the brake pedal, slacken the switch top
and bottom mounting nuts, then remove the
bottom nut completely. Disconnect the wiring
plug and vacuum hose from the switch and
remove it.
7The clutch pedal switch is mounted in a
spring-loaded bracket to allow for small
changes in pedal position with the operation of
the self-adjusting mechanism. Disconnect the
wiring plug and vacuum hose, then push the
switch out of its bracket.
8Refit by reversing the removal operations.
Adjust the switch position so that there is a
gap of at least 1.5 mm (0.06 in) between the
switch plunger cap and the body of the switch
(see illustration).
28Speed control system
components - removal and
refitting
Body electrical system 13•19
13
27.16 Removing the coolant level switch27.19 Removing the washer fluid level
switch27.22 Auxiliary warning system control
assembly - retaining nuts arrowed
27.27 Removing the auxiliary warning
system control module27.30 The bulb failure module secured to
the under-dash trim28.8 Vacuum dump valve/switch (B)
X = 1.5 mm (0.06 in) minimum
procarmanuals.com
The vehicle owner who does his or her own maintenance according
to the recommended service schedules should not have to use this
section of the manual very often. Modern component reliability is such
that, provided those items subject to wear or deterioration are
inspected or renewed at the specified intervals, sudden failure is
comparatively rare. Faults do not usually just happen as a result of
sudden failure, but develop over a period of time. Major mechanical
failures in particular are usually preceded by characteristic symptoms
over hundreds or even thousands of miles. Those components which
do occasionally fail without warning are often small and easily carried
in the vehicle.With any fault-finding, the first step is to decide where to begin
investigations. Sometimes this is obvious, but on other occasions, a
little detective work will be necessary. The owner who makes half a
dozen haphazard adjustments or replacements may be successful in
curing a fault (or its symptoms), but will be none the wiser if the fault
recurs, and ultimately may have spent more time and money than was
necessary. A calm and logical approach will be found to be more
satisfactory in the long run. Always take into account any warning
signs or abnormalities that may have been noticed in the period
preceding the fault - power loss, high or low gauge readings, unusual
smells, etc - and remember that failure of components such as fuses or
REF•5Fault Finding
Engine1
m mEngine fails to rotate when attempting to start
m mStarter motor turns engine slowly
m mEngine rotates, but will not start
m mEngine difficult to start when cold
m mEngine difficult to start when hot
m mStarter motor noisy or excessively-rough in engagement
m mEngine starts, but stops immediately
m mEngine idles erratically
m mEngine misfires at idle speed
m mEngine misfires throughout the driving speed range
m mEngine hesitates on acceleration
m mEngine stalls
m mEngine lacks power
m mEngine backfires
m mOil pressure warning light illuminated with engine running
m mEngine runs-on after switching off
m mEngine noises
Cooling system2
m
mOverheating
m mOvercooling
m mExternal coolant leakage
m mInternal coolant leakage
m mCorrosion
Fuel and exhaust systems3
m
mExcessive fuel consumption
m mFuel leakage and/or fuel odour
m mExcessive noise or fumes from exhaust system
Clutch4
m
mPedal travels to floor - no pressure or very little resistance
m mClutch fails to disengage (unable to select gears)
m mClutch slips (engine speed increases, with no increase in vehicle
speed)
m mJudder as clutch is engaged
m mNoise when depressing or releasing clutch pedal
Manual gearbox5
m
mNoisy in neutral with engine running
m mNoisy in one particular gear
m mDifficulty engaging gears
m mJumps out of gear
m mVibration
m mLubricant leaks
Automatic transmission6
m
mFluid leakage
m mTransmission fluid brown, or has burned smellm mGeneral gear selection problems
m mTransmission will not downshift (kickdown) with accelerator fully
depressed
m mEngine will not start in any gear, or starts in gears other than Park
or Neutral
m mTransmission slips, shifts roughly, is noisy, or has no drive in
forward or reverse gears
Propeller shaft7
m
mClicking or knocking noise on turns (at slow speed on full-lock)
m mVibration when accelerating or decelerating
Final drive and driveshafts8
m
mExcessive final drive noise
m mOil leakage from final drive
m mGrating, knocking or vibration from driveshafts
Braking system9
m
mVehicle pulls to one side under braking
m mNoise (grinding or high-pitched squeal) when brakes applied
m mExcessive brake pedal travel
m mBrake pedal feels spongy when depressed
m mExcessive brake pedal effort required to stop vehicle
m mJudder felt through brake pedal or steering wheel when braking
m mPedal pulsates when braking hard
m mBrakes binding
m mRear wheels locking under normal braking
Suspension and steering systems10
m
mVehicle pulls to one side
m mWheel wobble and vibration
m mExcessive pitching and/or rolling around corners, or during braking
m mWandering or general instability
m mExcessively-stiff steering
m mExcessive play in steering
m mLack of power assistance
m mTyre wear excessive
Electrical system11
m
mLights inoperative
m mIgnition/no-charge warning light remains illuminated with engine
running
m mIgnition/no-charge warning light fails to come on
m mBattery will not hold a charge for more than a few days
m mInstrument readings inaccurate or erratic
m mHorn inoperative, or unsatisfactory in operation
m mWindscreen/tailgate wipers inoperative, or unsatisfactory in
operation
m mWindscreen/tailgate washers inoperative, or unsatisfactory in
operation
m mElectric windows inoperative, or unsatisfactory in operation
m mCentral locking system inoperative, or unsatisfactory in operation
Introduction
procarmanuals.com
REF•6
Engine fails to rotate when attempting to start
m mBattery terminal connections loose or corroded (Chapter 1).
m mBattery discharged or faulty (Chapter 5).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapter 5).
m mDefective starter solenoid or switch (Chapter 5).
m mDefective starter motor (Chapter 5).
m mStarter pinion or flywheel/driveplate ring gear teeth loose or broken
(Chapters 2 or 5).
m mEngine earth strap broken or disconnected.
Starter motor turns engine slowly
m
mPartially-discharged battery (recharge, use jump leads, or push
start) (Chapter 5).
m mBattery terminals loose or corroded (Chapter 1).
m mBattery earth to body defective (Chapter 5).
m mEngine earth strap loose.
m mStarter motor (or solenoid) wiring loose (Chapter 5).
m mStarter motor internal fault (Chapter 5).
Engine rotates, but will not start
m
mFuel pump inertia switch tripped (electric pump) (Chapter 4).
m mFuel tank empty.
m mBattery discharged (engine rotates slowly) (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 1).
m mIgnition components damp or damaged (Chapters 1 and 5).
m mBroken, loose or disconnected wiring in the ignition circuit
(Chapters 1 and 5).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFuel injection system fault (Chapter 4).
m mMajor mechanical failure (eg broken timing chain) (Chapter 2).
Engine difficult to start when cold
m
mBattery discharged (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 1).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFuel injection system fault (Chapter 4).
m mOther ignition system fault (Chapters 1 and 5).
m mLow cylinder compressions (Chapter 2).
Engine difficult to start when hot
m
mAir filter element dirty or clogged (Chapter 1).
m mFuel injection system fault (Chapter 4).
m mLow cylinder compressions (Chapter 2).
Starter motor noisy or excessively-rough in
engagement
m mStarter pinion or flywheel/driveplate ring gear teeth loose or broken
(Chapters 2 or 5).
m mStarter motor mounting bolts loose or missing (Chapter 5).
m mStarter motor internal components worn or damaged (Chapter 5).
Engine starts, but stops immediately
m
mLoose or faulty electrical connections in the ignition circuit
(Chapters 1 and 5).
m mVacuum leak at the throttle body or inlet manifold (Chapter 4).
m mFuel injection system fault (Chapter 4).
Engine idles erratically
m
mCarburettor stepper motor plunger dirty (2.0 litre only) (Chapter 5)
m mIncorrectly-adjusted idle speed (Chapter 4).
m mAir filter element clogged (Chapter 1).
m mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mUneven or low cylinder compressions (Chapter 2).
m mCamshaft lobes worn (Chapter 2).
m mFuel injection system fault (Chapter 4).
Engine misfires at idle speed
m
mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty spark plug HT leads (Chapter 5).
m mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mFuel injection system fault (Chapter 4).
m mDistributor cap cracked or tracking internally, where applicable
(Chapter 5).
m mUneven or low cylinder compressions (Chapter 2).
m mDisconnected, leaking, or perished crankcase ventilation hoses
(Chapter 4).
Fault Finding
spark plugs may only be pointers to some underlying fault.
The pages which follow provide an easy-reference guide to the more
common problems which may occur during the operation of the
vehicle. These problems and their possible causes are grouped under
headings denoting various components or systems, such as Engine,
Cooling system, etc. The Chapter and/or Section which deals with the
problem is also shown in brackets. Whatever the fault, certain basic
principles apply. These are as follows:
Verify the fault. This is simply a matter of being sure that you know
what the symptoms are before starting work. This is particularly
important if you are investigating a fault for someone else, who may
not have described it very accurately.
Don’t overlook the obvious. For example, if the vehicle won’t start, is
there fuel in the tank? (Don’t take anyone else’s word on this particular
point, and don’t trust the fuel gauge either!) If an electrical fault isindicated, look for loose or broken wires before digging out the test
gear.
Cure the disease, not the symptom. Substituting a flat battery with a
fully-charged one will get you off the hard shoulder, but if the
underlying cause is not attended to, the new battery will go the same
way. Similarly, changing oil-fouled spark plugs for a new set will get
you moving again, but remember that the reason for the fouling (if it
wasn’t simply an incorrect grade of plug) will have to be established
and corrected.
Don’t take anything for granted. Particularly, don’t forget that a
“new” component may itself be defective (especially if it’s been rattling
around in the boot for months), and don’t leave components out of a
fault diagnosis sequence just because they are new or recently-fitted.
When you do finally diagnose a difficult fault, you’ll probably realise
that all the evidence was there from the start.
1 Engine
procarmanuals.com
Engine misfires throughout the driving speed range
m mFuel filter choked (Chapter 1).
m mFuel pump faulty, or delivery pressure low (Chapter 4).
m mFuel tank vent blocked, or fuel pipes restricted (Chapter 4).
m mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty spark plug HT leads (Chapter 5).
m mDistributor cap cracked or tracking internally (Chapter 5).
m mFaulty ignition coil (Chapter 5).
m mUneven or low cylinder compressions (Chapter 2).
m mFuel injection system fault (Chapter 4).
Engine hesitates on acceleration
m
mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mFuel injection system fault (Chapter 4).
Engine stalls
m
mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mFuel filter choked (Chapter 1).
m mFuel pump faulty, or delivery pressure low (Chapter 4).
m mFuel tank vent blocked, or fuel pipes restricted (Chapter 4).
m mFuel injection system fault (Chapter 4).
Engine lacks power
m
mFuel filter choked (Chapter 1).
m mFuel pump faulty, or delivery pressure low (Chapter 4).
m mUneven or low cylinder compressions (Chapter 2).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mFuel injection system fault (Chapter 4).
m mBrakes binding (Chapters 1 and 10).
m mClutch slipping (Chapter 6).
Engine backfires
m
mVacuum leak at the throttle body, inlet manifold or associated hoses
(Chapter 4).
m mFuel injection system fault (Chapter 4).
Oil pressure warning light illuminated with engine
running
m mLow oil level, or incorrect oil grade (Chapter 1).
m mFaulty oil pressure sensor (Chapter 2).
m mWorn engine bearings and/or oil pump (Chapter 2).
m mExcessively high engine operating temperature (Chapter 3).
m mOil pressure relief valve defective (Chapter 2).
m mOil pick-up strainer clogged (Chapter 2).
Note:Low oil pressure in a high-mileage engine at tickover is not
necessarily a cause for concern. Sudden pressure loss at speed is far
more significant. In any event, check the gauge or warning light sender
before condemning the engine.
Engine runs-on after switching off
m mExcessive carbon build-up in engine (Chapter 2).
m mExcessively high engine operating temperature (Chapter 3).
Engine noises
Pre-ignition (pinking) or knocking during acceleration or
under load
m mIgnition timing incorrect/ignition system fault (Chapters 1 and 5).
m mIncorrect grade of spark plug (Chapter 1).
m mIncorrect grade of fuel (Chapter 1).
m mVacuum leak at throttle body, inlet manifold or associated hoses
(Chapter 4).
m mExcessive carbon build-up in engine (Chapter 2).
m mFuel injection system fault (Chapter 4).
Whistling or wheezing noises
m
mLeaking inlet manifold or throttle body gasket (Chapter 4).
m mLeaking exhaust manifold gasket (Chapter 4).
m mLeaking vacuum hose (Chapters 4 and 10).
m mBlowing cylinder head gasket (Chapter 2).
Tapping or rattling noises
m
mWorn valve gear, timing chain, camshaft or hydraulic tappets
(Chapter 2).
m mAncillary component fault (water pump, alternator, etc) (Chapters 3,
5, etc).
Knocking or thumping noises
m mWorn big-end bearings (regular heavy knocking, perhaps less under
load) (Chapter 2).
m mWorn main bearings (rumbling and knocking, perhaps worsening
under load) (Chapter 2).
m mPiston slap (most noticeable when cold) (Chapter 2).
m mAncillary component fault (water pump, alternator, etc) (Chapters 3,
5, etc).
REF•7Fault Finding
2Cooling system
Overheating
m
mAuxiliary drivebelt broken or incorrectly adjusted (Chapter 1).
m mInsufficient coolant in system (Chapter 1).
m mThermostat faulty (Chapter 3).
m mRadiator core blocked, or grille restricted (Chapter 3).
m mElectric cooling fan or thermostatic switch faulty (Chapter 3).
m mViscous-coupled fan faulty (Chapter 3).
m mIgnition timing incorrect, or ignition system fault (Chapters 1 and 5).
m mInaccurate temperature gauge sender unit (Chapter 3).
m mAirlock in cooling system (Chapter 3).
Overcooling
m
mThermostat faulty (Chapter 3).
m mInaccurate temperature gauge sender unit (Chapter 3).
External coolant leakage
m
mDeteriorated or damaged hoses or hose clips (Chapter 1).
m mRadiator core or heater matrix leaking (Chapter 3).
m mPressure cap faulty (Chapter 3).
m mWater pump internal seal leaking (Chapter 3).
m mWater pump-to-block seal leaking (Chapter 3).
m mBoiling due to overheating (Chapter 3).
m mCore plug leaking (Chapter 2).
Internal coolant leakage
m
mLeaking cylinder head gasket (Chapter 2).
m mCracked cylinder head or cylinder block (Chapter 2).
Corrosion
m
mInfrequent draining and flushing (Chapter 1).
m mIncorrect coolant mixture or inappropriate coolant type (Chapter 1).
procarmanuals.com